Fix OOB read in TS_OBJ_print_bio().

TS_OBJ_print_bio() misuses OBJ_txt2obj: it should print the result
as a null terminated buffer. The length value returned is the total
length the complete text reprsentation would need not the amount of
data written.

CVE-2016-2180

Thanks to Shi Lei for reporting this bug.

Reviewed-by: Matt Caswell <matt@openssl.org>

crypto/ts/ts_lib.c

@@ -40,9 +40,8 @@ int TS_OBJ_print_bio(BIO *bio, const ASN1_OBJECT *obj)
 {
     char obj_txt[128];
 
-    int len = OBJ_obj2txt(obj_txt, sizeof(obj_txt), obj, 0);
-    BIO_write(bio, obj_txt, len);
-    BIO_write(bio, "\n", 1);
+    OBJ_obj2txt(obj_txt, sizeof(obj_txt), obj, 0);
+    BIO_printf(bio, "%s\n", obj_txt);
 
     return 1;
 }